General conditions are derived for the essential self-adjointness of -
DELTA + V, where V is a translation-invariant random potential, and fo
r the existence of the perturbation expansion. A sequence of graphs is
exhibited violating Dell'Antonio's bound for skeleton graphs. For a t
ranslation-invariant and clustering Gaussian random potential V, and a
translation-invariant and clustering initial state S of the Fermi gas
, uncorrelated with the random potential, the weak coupling limit (Van
Hove limit) yields increase of entropy, propagation of chaos, converg
ence of the state for sufficiently small values of the parameter T to
a gauge-invariant and quasi-free asymptotic state, and the semigroup d
escribing the evolution of the two-point function. The asymptotic syst
em is Bernoulli. Results are obtained not only for the average over th
e random potential but also with probability one. If the random potent
ial V' is absolutely continuous with respect to V, and if the state S'
is given by a density matrix in the GNS representation for S, then th
e weak coupling limit is the same as for V and S.